Synthetic filaments are traditionally produced by various spinning techniques. For example, synthetic filaments may be melt-spun by extruding a melt spinnable polymer through relatively small-sized orifices in a spin pack to form a stream of filaments. The filaments are substantially immediately solidified by passing a cross-flow of solidification fluid (e.g., air) through a quench cabinet. The filaments are thereafter continuously taken up by a high speed winder to form a generally cylindrical package.
Conventional spin packs may include a number of spin pots, each of which in turn includes a polymer filter (e.g., screen packs), a polymer distribution plate and a spinneret plate in that order. The polymer filter, distribution plate and spinneret plate are held in a housing pot that may be removed from the spin pack to allow servicing and/or replacement of the individual structural components of the spin pot.
Oftentimes, the flow through spinneret holes become blocked due to contamination that is present in the system downstream of the filter. In this regard, the polymer filters are typically formed of a sintered metal (i.e., so-called Mott filters in accordance with U.S. Pat. Nos. 3,570,059 and 3,802,821, the entire content of each being expressly incorporated hereinto by reference). Thus, particles of such sintered metal from the Mott filters and/or other debris that may remain from the filter cleaning operation can be dislodged and carried downstream with the polymer flow where they block one or more spinneret holes. These blocked spinneret holes are known colloquially in the art as "slow-holes" since the polymer flow therethrough is impeded. When slow-holes occur, the entire spinning line must be shut down in order to prevent the production of off-specification product.
It would therefore be desirable if the occurrence of such slow-holes could be minimized or eliminated entirely. It is towards providing such a solution that the present invention is directed.
Broadly, the present invention is embodied in synthetic filament spin pots and methods of spinning synthetic filaments which employ an electroformed perforated screen downstream of the polymer filter. In this regard, the perforated screen serves to remove debris from the polymer screen that may exist downstream of the polymer filter unit (e.g., debris that may be dislodged from the filter unit, or parts of the filter unit itself) so as to significantly minimize the occurrence of "slow-holes" in the spinning line.
Other aspects and advantages of the present invention will become more clear from the following detailed description of the preferred exemplary embodiments thereof which follow.